Appendix V. IOOI rigidly connected at front and back, and by extra stays near the engine. The dashboard is at c, and the engine bonnet at /£, the latter pierced with Venetian openings for coolness, while d is a lubricator leading oil to all main machine parts. The wheels are of ' artillery' pattern, in imitation of those used on gun-carriages, and are generally supplied with pneumatic tyres, pumped to 100 Ibs. pressure. The axles wand x are ' dead/ that is, are prevented from rotation, the wheels merely revolving on the tapered axle ends ; but one form of car has a * live * hind axle driven by bevel gear at its mid-length by a shaft from the gear box having universal joints in its length. The distribution of weight is such as to put nearly equal loads on front and back wheels, when working; and as the engine and radiator are most conveniently placed in the front, the gear-case and water tank are put in the rear, although this neces- sitates considerably extra weight in pipes. The petrol tank is at *?, and the fuel feeds therefrom to the carburettor B, where it is gasified and mixed with air before passing to the cylinders A A by the inlet pipes h h. The exhaust pipes then carry the products to the silencer, where they enter at R, pass backward and forward through concentric cylinders, and emerge at s. The engines are usually of the vertical type, with crank chambers underneath, although horizontal types have sometimes been introduced to overcome vibration. The former is, however, most convenient, and if several cylinders are used with pistons travelling in opposite directions, the inertia forces may be fully balanced (see B, Fig. 860, p. 898). The 'tourist' car shewn, of 12 to 15 B.H.P., requires four cylinders, and in addition a large fly-wheel c to equalise crank effort, into which is fitted the friction clutch D. Earlier cars were often belt-driven, which provided a perfect slipping arrangement for obtaining half power and the necessary fine adjustment between change of gears, but belts are much affected by change of weather, and cause much difficulty when riding up hills. The friction clutch is an admitted necessity, and is kept in gear by a strong spring E, giving uniform but not over- grip, which can be released by a foot lever wholly or partially, thus providing the required 'elasticity' of power, only perfectly obtained in the steam engine.